Circuit design involves deep study of manufacturer's data sheets for each component to ensure it is applied correctly. It typically requires creation of a schematic symbol for each of the less common components, then graphically drawing a circuit schematic, a process called "schematic capture". Many pages of spreadsheet calculations will be done to determine circuit parameters and to check that component ratings are not exceeded. Manufacturer and part number information will be entered into the schematic for every component. This circuit schematic is the central “source” from which the BOM and PCB netlist will be generated. It is also used to render the schematic diagram in PDF form.